Intelligence and Miscellaneous Articles. 317 



ration of aurate of potash, but at high temperature it quickly re- 

 duces it to the metallic state. 



Auric acid assumes different colours according to its condition as 

 a hydrate. Thus prepared with aurate of barytes, or with magnesia, 

 or carbonate of soda, it is of an ochre-brown ; when precipitated cold 

 from chloride of gold by potash not in excess, it is canary-yellow ; 

 precipitated from aurate of potash by a weak acid, as the carbonic, 

 or by very dilute sulphuric or nitric acid, it is also canary-yellow. 

 If the acid be concentrated, it is of an olive colour, and seems of so 

 deep a green that it appears black. Nitric and sulphuric acids of a 

 common degree of dilution precipitate it from the solution of aurate 

 of potash of a deep yellow colour ; the differences of colour depend 

 in all cases on the proportion of water contained in these oxides, for 

 they are all of similar composition, containing 10 per cent, of 

 oxygen. 



Aurate of Potash. — In order that auric acid may dissolve readily 

 in potash, it must be obtained in the gelatinous state, by the decom- 

 position of an aurate ; the solution is with difficulty evaporated so as 

 to prevent the precipitation of protoxide of gold ; the only method 

 by which Mr, Figuier could succeed in obtaining it free from prot- 

 oxide was that of exposing very small quantities to spontaneous eva- 

 poration. This salt is of a greenish -yellow colour, very soluble in 

 water and in alcohol ; the alcoholic solution suffers no change by 

 exposure to the air ; but if it be heated to 112°F., the whole of the 

 gold is immediately precipitated of a brown colour. — Ann. de Ch. et 



de Phys., Juillet 1844. 



ON THE PREPARATION AND PROPERTIES OF CERTAIN CHLO- 

 RATES. BY M. ALEXANDER WAECHTER. 



Protochlorate of Mercury. — Recently precipitated protoxide of 

 mercury was dissolved in chloric acid ; the solution, evaporated over 

 sulphuric acid, yielded fine prismatic crystals to the last drop ; but 

 they quickly lost their transparency and splendour, and became dull 

 by exposure to the air. Water and alcohol readily dissolve the unal- 

 tered crystals, without leaving any residue ; they also dissolve those 

 which are altered, but leave a small white residue, which becomes 

 black by ebullition. If this salt be triturated with water and chloride 

 of sodium, a white precipitate is obtained, and the supernatant liquor 

 has a neutral reaction. The salt is therefore a neutral chlorate of the 

 protoxide of mercury. If it be heated it loses oxygen at 482° F., 

 and is converted into a mixture of binoxide and bichloride of mer- 

 cury ; the latter may be separated by sublimation at 563° F., and the 

 first remains if the temperature do not exceed 698°. If it be heated 

 rapidly, the decomposition takes place suddenly, and chlorine is one 

 of the products of the decomposition. 



When the solution of this salt is evaporated to dryness by the 

 water-bath, and the crystalline mass remaining is treated with water, 

 an insoluble modification is obtained, already described by Vauquelin, 

 as a white insoluble powder ; this salt, triturated with water and 

 chloride of sodium, yielded also a white precipitate of calomel, it was 

 not therefore a basic salt, and it was completely dissolved in acetic 

 acid. All the mercury was precipitated in the state of calomel from 



